The pseudo-conformal universe: scale invariance from spontaneous breaking of conformal symmetry

Journal Article · Sun Apr 01 00:00:00 EDT 2012 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2012/04/023· OSTI ID:22279776

Hinterbichler, Kurt; Khoury, Justin ^[1]

---

1. Center for Particle Cosmology, Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)

We present a novel theory of the very early universe which addresses the traditional horizon and flatness problems of big bang cosmology and predicts a scale invariant spectrum of perturbations. Unlike inflation, this scenario requires no exponential accelerated expansion of space-time. Instead, the early universe is described by a conformal field theory minimally coupled to gravity. The conformal fields develop a time-dependent expectation value which breaks the flat space so(4,2) conformal symmetry down to so(4,1), the symmetries of de Sitter, giving perturbations a scale invariant spectrum. The solution is an attractor, at least in the case of a single time-dependent field. Meanwhile, the metric background remains approximately flat but slowly contracts, which makes the universe increasingly flat, homogeneous and isotropic, akin to the smoothing mechanism of ekpyrotic cosmology. Our scenario is very general, requiring only a conformal field theory capable of developing the appropriate time-dependent expectation values, and encompasses existing incarnations of this idea, specifically the U(1) model of Rubakov and the Galileon Genesis scenario. Its essential features depend only on the symmetry breaking pattern and not on the details of the underlying lagrangian. It makes generic observational predictions that make it potentially distinguishable from standard inflation, in particular significant non-gaussianities and the absence of primordial gravitational waves.

• OSTI ID: 22279776
• Journal Information: Journal of Cosmology and Astroparticle Physics, Vol. 2012, Issue 04; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
APPROXIMATIONS
ATTRACTORS
CONFORMAL INVARIANCE
COSMOLOGY
DE SITTER GROUP
DE SITTER SPACE
DISTURBANCES
EXPECTATION VALUE
GRAVITATIONAL WAVES
LAGRANGIAN FUNCTION
METRICS
POTENTIALS
QUANTUM FIELD THEORY
SCALE INVARIANCE
SPACE-TIME
SYMMETRY BREAKING
TIME DEPENDENCE
UNIVERSE